Hearing aid



FIG. 1 is a front elevational view of a hearing aid showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a side elevational view thereof, the broken line showing of an adaptor is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a hearing aid, as shown and described. 